1. Field of the Invention
The present invention relates to a process cartridge for use in an image forming apparatus using an electrophotography method, such as a laser printer or a copying machine, and to an electrophotographic image forming apparatus.
2. Related Background Art
An electrophotographic image forming apparatus forms an image on a recording medium by using electrophotography. Examples of an electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (laser beam printer, LED printer and the like), a facsimile machine, and a word processor.
Generally speaking, a process cartridge is obtained by integrating a charging means, a developing means, or a cleaning means as a process means with an electrophotographic photosensitive member to form a cartridge which is detachable with respect to an image forming apparatus main body. Apart from this, a process cartridge is obtained by integrating at least one of a charging means, a developing means, and a cleaning means as process means with an electrophotographic photosensitive member to form a cartridge which is detachable with respect to an image forming apparatus main body, or by integrating at least a developing means as a process means with an electrophotographic photosensitive member to form a cartridge which is detachable with respect to an image forming apparatus main body.
A drum unit is a unit including a photosensitive drum which is an electrophotographic photosensitive member in a process cartridge which is detachable with respect to an electrophotographic image forming apparatus main body.
Conventionally, an image forming apparatus using the electrophotographic-image-forming process adopts a process-cartridge system, in which an electrophotographic photosensitive member and a process device described above are integrated into a cartridge which is detachable with respect to an image forming apparatus main body. In the process-cartridge system, the maintenance of the apparatus can be performed by the user without depending on a serviceman, thereby achieving a marked improvement in operability. Thus, the process-cartridge system is widely applied to image forming apparatuses.
By adopting the process-cartridge system, the user can easily perform maintenance and replacement whenever the process device needs maintenance, making it possible to obtain a high quality image at a low cost and with ease.
FIGS. 30 and 31 show a conventional electrophotographic image forming apparatus using the process-cartridge system. This process cartridge 502 is composed of two units: a drum unit 510 including a drum-frame body 513 integrally supporting a photosensitive drum 511, a charging roller 507, a cleaning blade 512a, etc., and a developing unit 520 including a developing-frame body 523 integrally supporting a developing roller 521 and a developing blade 522 and a toner container (container-frame body) 524 containing toner serving as the developer.
To integrally join the two units, side covers 530 and 540 are fixed to the side surfaces of the units by means of screws 551 through 554 to form integrally a cartridge.
The above-described process cartridge has the following problems:
First, due to the construction in which the drum-frame body, the toner container, etc. are held between the side covers and fastened by screws, the requisite number of screws for fixing the side covers is rather large, resulting in an increase in assembly man-hours.
Further, due to a variation in the longitudinal dimensions of the frame bodies of the two units of the process cartridge, there is the possibility of the drum unit and the developing unit being connected in parallel and obliquely.